1. Field of the Invention
This invention relates to radiation processing of heavy oils.
2. Background of the Invention
Heavy oils are petroleum deposits that hold promise for the large scale production of products that can be utilized as fuel oil and petroleum based products. Ultimately, heavy oil and bitumen are used to make the same petroleum products as conventional forms of crude oil; however, more processing is required. In 2002, heavy oil, synthetic oil and crude bitumen accounted for almost 60 percent of total Canadian crude oil production. (Canadian Centre for Energy Information, web page, 2006). Canadian reserves include the tar sands fields near Ft. McMurray Alberta, Canada (estimated to contain 174-311 billion recoverable barrels).
Large deposits also occur in Russia, Khazakstan (such as the Kumkol, Karazhanbas (311 Million barrels; Zaykina et al. Rad. Phys. Chem. 20:211-221, 2001; Zaykin, Zaykina and Silverman, Rad. Phys. Chem. 69:229-238, 2004), and Akshabulak fields (oil sands)), Brazil, USA (in the form of shale oils), and bitumen from Mexico and from the Orinoco Belt in Venezuela (estimated to contain 200-270 Billion barrels). However, their viscosity limits their use and methods to lower viscosity can be both costly and harmful to the environment. These oil resources, however, require three to four times the cost of conventional light oil to extract and can have detrimental effects on the environment.
Extraction of heavy oil petroleum deposits often involves heating a heavy oil mixture, such as in U.S. Pat. No. 7,077,198, wherein one or more heat sources may be used to heat a portion of the hydrocarbon containing formation (shale oil) to temperatures that allow pyrolysis of the hydrocarbons.
Paraffinic polymers such as polyethylene undergo degradation when exposed to low dose rates of ionizing radiation while in the presence of air. (Charlesby A., J. Am. Chem Soc., pp. 60-74, 1953) The degradation products and their yields are a function of the dose, dose rate, oxygen concentration, temperature, polymer morphology, branching ratio, degree of unsaturation and polymer processing additives. While the literature is not extensive enough to provide a detailed model that takes into account all these factors and their nonlinear interactions, it is clear that the information currently available can be profitably applied to a related but more important problem, namely, the radiation-induced oxidative conversion of heavy liquid paraffinic petroleum to products with lower molecular weight distribution.
Published works describe poor success in using ionizing radiation to “degrade” the paraffins; the emphasis in all such works is on high dose rate and/or high temperature and pressure. (Petermann and Gleiter, Kolloid-Z u. Z. Polymere 251:850-856, 1973; Ungar and Keller, Polymer, 21:1273-1277, 1980: Katsumura, Y. Die Angewandte Malcromolekulare Chemie 252:89-101, 1997; Seguchi, T. et al., Rad. Phys. Chem. 37:29-35, 1991) The results are so unpromising as to lead one of the leading experimentalists in the field to declare that normal paraffinic oils and polymers are for all practical purposes inert to ionizing radiation. (Review in: “A literature Review on Cold Cracking of Petroleum Crude Oil,” U.S. Dept. of Energy, July 2006). Seguchi et al. (ibid, page 35) stated that n-paraffins should behave similarly to polyethylene and state that there is “no clear evidence that main-chain scission occurs in linear polyethylene upon irradiation” and “main chain scission in both polyethylene and ethylenepropylene copolymer is negligible.”
Much of the current literature describes either eliminating or reducing paraffinic oils or dewaxing processes for producing very high viscosity index, low pour point lubricating oil base stocks from a mineral oil feed (see U.S. Pat. No. 7,074,320).
Electron beam technology has been used in the treatment of contaminated liquids (see U.S. Pat. No. 5,807,491) and has been suggested for the processing of liquids, including petroleum products (see U.S. Pat. No. 5,530,255). Zaykina et al. (2001, ibid) show temperature and dose rate effects on the radiation chemistry of oil from the Karazhanbas oil field. For experiments utilizing a temperature of 450° C., and a dose rate of 5 kGy/sec, doses up to 6 kGy resulted in isomerization, whereas at 375° C. and a dose rate of 25 kGy/sec, the same doses led to “intense molecular destruction.” Mirkin et al., (Rad. Phys. Chem. 67:311-314, 2003) and Zaykin et al., (Rad. Phys. Chem. 67: 305-309, 2003) discuss the use of temperatures of 350-420° C., and a pressure of nearly 1 atm. Zaykin and Zaykina, (Rad. Phys. Chem. 71:469-472, 2004) discusses thermal processing at 350° C. with a combination of ozonolysis and irradiation with 2 MeV electrons from a linear accelerator. The U.S. Department of Energy report (Ibid, page 13, 2006) asserts that the analysis in the Zaykin et al. 2004 study included high octane gasoline due to the presence of a higher isoparaffin content, but “lacked a quantitative mass balance to account for the other hydrocarbon fractions” and “the stability of the gasoline fraction was not reported.”
Zaykin et al., (Zaykin, Zaykina and Silverman, Rad. Phys. Chem., 69:229-238, 2004) discusses the radiation-thermal conversion of paraffinic oils using 340-350° C. and irradiation in the range of 1-4 kGy/sec, and states that the paraffinic residue had a “strong tendency to polymerization” under these conditions. At irradiation doses of 1.4 and 2 kGy and dose rates above 2 kGy/sec, the results show the presence of a small light molecular weight fraction whose yield increases with dose rate. The Department of Energy report (Ibid, page 13, 2006) states that the Zaykin (Rad. Phys. Chem. 69:229-238, 2004) article showed the irradiation of the paraffinic Kumkol crude sample with a high paraffinic oil content tended to polymerize and that the samples had 10-15% of the mass as emulsified water, which could have greatly impacted the results. KZ Patent Application No. 970915.1 (Zaikina et al.) discloses a method for refining processed and residual petroleum using temperatures of 240-450° C., a dose of 1-80 kGy, and a dose rate of 1-60 kGy/s. KZ Patent Application No. 990377.1 (Zaikina et al.) discloses a method of purification of hydrocarbon resources in order to remove sulphurous compounds, using 10-100 kGy, a 0.1-10.0 kGy/sec dose rate and a temperature of 200-400° C. RU 2,142,496 to Pavlovich discloses a charged particle accelerator and working chamber for introducing a particle beam for the processing of petroleum products.
(see also: Kazakhstan Patent No. 970915.1 to Zaykina et al; and 990377.1 to Zaykina et al; and Russian Patent No. RU 2,142,496 to Pavlovich).
There exists a need for a method to efficiently extract and process heavy oils into light petroleum products that is cost effective, high yield and environmentally friendly.